The most important objectives of wireless communications, broadcasting, telemetry, infrared and in general “radio” systems as well as “wired” systems include: power and bandwidth or spectrum efficiency combined with robust Bit Error Rate (BER) performance in a noisy and/or strong interference environment. These Radio Frequency (RF) system objectives are specified in numerous systems including wireless communications and cellular systems, satellite systems, mobile and telemetry systems, broadcasting systems, cable, fiber optics and practically all communication transmission systems. Here we are using the term “Radio Frequency” (RF) in its broadest sense, implying that we are dealing with a modulated signal. The RF could be, for example, as high as the frequency of infrared or fiber optic transmitters; it could be in the GHz range, e.g., between 1 GHz and 300 GHz, or it could be in the MHz range, e.g. between about 1 MHz and 999 MHz or just in the kHz range. The term RF could even apply to Quadrature Modulated (for short “QM” or “QMOD”) Base-Band (BB) signals.
The cited publications-references [1-24], patents [P1-P10], and the references within the aforementioned publications contain definitions and descriptions of many terms used in this new patent disclosure and for this reason these “prior art” terms and definitions will be only briefly, on a case by case basis highlighted. Robust or high performance BER specifications and/or objectives are frequently expressed in terms of the required BER as a function of Energy per Bit (Eb) divided by Noise Density (No), that is, by the BER=f(Eb/No) expression. Cost, reduced size, compatibility and interoperability/compatibility with other conventional or previously standardized systems, also known as “legacy systems,” are highly desired. Several standardization organizations have adopted modulation techniques such as conventional Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), Offset Quadrature Phase Shift Keying (OQPSK), also designated as Staggered Quadrature Phase Shift Keying (SQPSK) and pi/4-QPSK techniques including differential encoding variations of the same. See publications [1-23] and referenced patents [P1-P8]. For spectrally or spectrum efficient (i.e., band-limited) signaling, these conventional methods exhibit a large envelope fluctuation of the modulated signal, and thus have a large increase in peak radiation relative to the average radiated power. For these reasons such systems are not suitable for Bit Rate Agile (BRA), robust BER performance NLA operated RF power efficient systems. Experimental work, computer simulation, and theory documented in many recent publications indicates that for bandlimited and standardized BPSK, QPSK, OQPSK or SQPSK or pi/4-QPSK, and QAM system specifications, very linear amplifiers are required to avoid the pitfalls of spectral restoration and of BER degradation. Linearized or linear amplifiers are less RF power efficient (during the power “on” state, power efficiency is defined as the transmit RF power divided by DC power), considerably more expensive and/or have less transmit RF power capability, are larger in size, and are not as readily available as NLA amplifiers. The advantages of NLA over Lin amplifiers are even more dramatic at higher RF frequencies, e.g. above 1 GHz for applications requiring low dc voltage, e.g., size “AA” batteries having only 1.5 Volt dc and for high RF modulated power requirements, e.g., transmit RF power in the 0.5 Watt to 100 Watt range.
Published prior art references [P1-P8] and [1-23] include additional background information. These references include descriptions of binary- and multiple-state Transmitter/Receiver (Transceiver) or for short (“TR”) systems that are suitable for NLA. These Modems and Transceivers have been designated as first generation of Feher patented Quadrature Shift Keying (FQPSK). For example, in reference [23] published on May 15, 1999 the authors Drs. M. K. Simon and T. Y. Yan of JPL/NASA-Caltech present a detailed study of Unfiltered Feher-Patented Quadrature Phase Shift Keying (FQPSK”. In references [1-21] and patents [P1-P8] numerous first generation FQPSK technology based terms, other than the FQPSK abbreviation/acronym have been used. In addition to FQPSK Transceivers, these first generation systems have also been described and/or defined as: Feher's Minimum Shift Keying (FMSK), Frequency Shift Keying (FFSK), Gaussian Minimum Shift Keying (FGMSK), Quadrature Amplitude Modulation (FQAM) and/or (F) Modulation/Amplification (FMOD). Additionally terms such as Superposed Quadrature Amplitude Modulation (SQAM), Intersymbol Interference and Jitter Free (IJF) and/or IJF-OQPSK have also been described in Feher et al.'s prior inventions and publications.
In the cited patents and references, among the aforementioned abbreviations, acronyms, designation, terms and descriptions the “FQPSK” abbreviation/term has been most frequently used to describe in most generic terms one or more of these Feher et al., previously described, first generation of Non-Linearly Amplified (NLA) inventions and technologies. The 1.sup.st and 2.sup.nd generation of FQPSK systems have significantly increased spectral efficiency and enhanced end-to-end performance as compared to other conventional NLA systems. RF power advantages, robust BER performance and NLA narrow spectrum without the pitfalls of NLA conventional BPSK and DBPSK, QPSK and OQPSK have been attained with these FQPSK systems. The aforementioned modulation and processing methods use data signal shaping methods whereby the data signals, also referred to as data bits, data symbols, signaling elements or signal wavelets, are shaped signals. Systems such as QPSK, FQPSK, QAM and FQAM could be interpreted as two dimensional modulation and transceiver systems whereby the information is contained in the amplitude and in the phase of the data symbols of the Quadrature Modulated (QM) signals.
The RF spectral efficiency of the aforementioned systems for four (4) state modulation systems, such as QPSK, DQPSK, SQPSK and FQPSK, is limited to 2 b/s/Hz, while the spectral efficiency of multi-state or multi-ary systems such as 64 state QAM is limited to 6 b/s/Hz. An increased number of signaling states increases the complexity of a transceiver and increases the required C/N, that is it has a negative impact on the BER=f(Eb/No) performance, as increased C/N requirement and increased Eb/No requirement leads to more expensive and larger transceivers and/or reduced fade margins. Among the highest spectral efficiencies attained with practical QAM type of systems are for 1024 state 1024-QAM systems with a theoretical limit for 1024-QAM of 10 b/s/Hz and practical limit of about 8 b/s/Hz. However, such a relatively high spectral efficiency requires very complex implementations, steep filters and a significantly increased C/N requirement.
Pulse Width Modulation (PWM) and Pulse Duration Modulation methods, described in Peebles's book [8] and in other prior art references, provide the signal information in the width and/or in the duration of the data symbols. However PWM and PDM methods have a very low spectral efficiency, and for this reason have not generally found applications in RF spectral efficient systems. H. R. Walker's patents [P9] and [P10] as well as Walker et al. publications, including [21] and [24] describe information signal transmission methods which could attain ultra high spectral efficiencies of more than 10 b/s/Hz. In one aspect, to the understnading of inventor, the Walker references appear to provide methods whereby the data information content is transmitted in the clock position, clock duration and/or in the location of one of the edges of the clock transitions. The focus in the Walker et al. references is on binary non-shaped two-level Non-Return to Zero (NRZ) and to Return to Zero (RZ) binary synchronous and symmetrical clocks and to embodiments in which the input data has a bit period of M clock periods, and the data bit polarity are phase shift key coded with waveform widths of M/M, M+1/M and M+2/M bit periods wherein M is an even integer greater than 3. Walker also appears to disclose a method for encoding an output encoded non-shaped signal clock incorporating polarity switches encoded at a plurality of time periods which are equal to and fractionally larger than the bit period of the NRZ data signal. In the aforementioned Walker methods the clock signals are not shaped and have the same basic form for the zero and one states respectively i.e., the Walker methods use NRZ or RZ type of symmetrical clock signals.
Some of the fundamental novelties of this Feher Keying (FK) invention, as compared to the aforementioned prior art references including the Walker et al. patents and publications, are briefly highlighted in this paragraph. Methods and implementation strategies and circuits which generate shaped symmetrical and non-symmetrical clock signals, two level and multilevel non-symmetrical clock signals, variable rise and different non-symmetrical fall time and/or other shaped clock signals and asynchronous clock signal information transmission means, where asynchronous clocking is referenced to the incoming data source signals are disclosed. In one of the embodiments of this invention the FK shaped and non-symmetrical format clock signals have different signal shapes for the one (1) state of that for the zero (0) state. The FK processors are also used in conjunction with NLA cross-correlated and Bit Rate Agile (BRA) quadrature FQPSK, FQAM and also non quadrature modem systems and as input drive signals to FM-VCO based systems to SSB to VSB to DSB-SC and in conjunction with conventional QPSK and QAM transceivers.
While the aforementioned issued patents and publications describe material of a background nature, they do not describe or suggest the subject matter of the present patent which provide novel enhanced performance systems and methods having more efficient and simpler bit rate agile and shaped clock modulation and transceiver demodulation agile/selectable technologies.